In computer memory, such as dynamic random-access memory (DRAM), incoming data (i.e., DQ) and command/address signals from a host suffer from intersymbol interference (ISI). Intersymbol interference can be caused by both channel bandwidth limitations and reflections. Intersymbol interference results in a closing of an eye response of a received signal.
To mitigate the effects of ISI, the Joint Electron Device Engineering Council (JEDEC) introduced decision feedback equalization (DFE) in the data buffer in DDR4 memory and in the data buffer and registered clock driver in DDR5. The actual implementation of DFE is undefined. A simple and robust method for implementing DFE is needed.
It would be desirable to implement a DFE open loop training for DDR data buffer and registered clock driver.